Resistance unit and method of producing the same



1931. c. H.' BOYLES 1,788,146

RESISTANCE UNIT AND METHOD OF PRODUCING THE SAME Filed April 30, 1928 Q-O/ Co3 INVEN TOR.

ATTORNEYS Patented Jan. 6, 1931 PATENT OFFICE CARROLL B. IBOYLES, OF MILWAUKEE, WISCONSIN RESISTANCE Um AND METHOD PRODUCING THE SAME Application filed April 80,

This invention relates to improvements in resistance units and method of producing the same.

It is one of the objects of this invention to 6 provide an improved resistance unit, which,

when energized, will radiate heat of great intensity such as is necessary in smelting furnaces, electric stoves and heaters, electric irons, and the like.

10 It is a further object of this invention to provide a novel method of producing this improved resistance unit.

It is a further object of this invention to provide a resistance unit having an outer coating of material which will prevent oxidation of the heating element within.

It is a further object of this invention to provide a resistance unit which is efiicient in operation, simple in construction, and well adapted for the purpose described.

With the above and other objects in view, the invention consists of the improved resistance unit and method of producing the, same, and all its parts and combinations as set forth in the claims, and all equivalents thereof.

In the accompanying drawing in which the same reference characters designate the same parts in all of the views:

Fig. 1 isa longitudinal sectional view of the improved reslstance unit;

Fig. 2 is a sectional view taken on the line 22 of Fig. 1; and

Fig. 3 is an end view thereof.

Referring to the drawing, the numeral 5 designates the heating element which is composed of a portion of gas carbon or amorphous carbon mixed witha portion of carbide of boron, the latter substance being thoroughly pulverized. These two ingredients are then mixed with a binding material such as coal tar or sodium silicate, and the compound is molded into the desired form, preferably the form shown. The molded product is next subjected to a high hydraulic pressure to render it as dense as possible, and is then heated to a temperature of 1200 F. to 1400 F. for a period of 24 to 48 hours to expel all volatile compounds. The exact proportions of the various ingredients used may be 1828. Serial No. 878,969.

varied in accordance with the resistance desired in the unit. The following is the formula used:

46% to 80% carbon, 52% to 12% carbide of boron, 2% to 8% sodium silicate. 55 Pulverized corundum may be substituted for the carbide of boron, and in the claims it is to be considered as the full equivalent of the latter substance.

The numeral 6 in the drawing designates the outer covering which is a non-conductor of electricity, and which prevents air from reaching the heating element within and oxidizing the latter. This outer coating is formed by mixing a quantity of pulverized corundum with,a suitable binder such as sodium silicate. The following proportions may be used: Y

85% to 98% corundum, 15% to 2% sodium sili 'Tfiformula may be varied by substituting pulverized carbide of boron for the corundum. The carbide of boron is to be con sidered as the full equivalent of corundum in the claims. After this compound has been prepared it is molded around the heating element and is subjected to a high pressure. The unit is then subjected to a temperature of 1800 to 2000 F. for a period of 18 to 36 hours to expel all remaining volatile compounds and to harden the unit.

The end portions 7 of the unit are referably composed of a material having a ow resistance to more readily conduct electricity. 35 If desired, this may be accomplished by coating the ends of the heating element with a conductor material such as co per, or the ends may be formed entirely 0? such material.

The ends 7 are of larger diameter than the heating element proper and are molded with it to form a spool-shaped core for the outer coating. J

From the foregoing description it may be seen that the improved resistance unit is simple in construction, efiicient, and well adapted for the urpose described.

What I c aim is:

1. As a new article of manufacture, a re- 1 element composed to pressure and sistance unit comprising an inner heating of 46-80% carbon, 52-12% carbide of boron and 2-8%binder, and an outer covering for a portion of the same composed posed of 85-98% corundum and 15-2% inder.

2. As a new article of manufacture, a resistance unit comprising an inner heating element composed of 46-80% carbon, 52-12% carbide of boron, and 2-8% sodium silicate, and an outer covering for a portion of the same composed of 85-98% corundum and 15-2% sodium silicate.

3. The method of roducing a resistance unit consisting of mixing together carbon, carbide of boron, and a blnder, molding the same into a desired form, subjecting the comund to the action of pressure and heat, mixmg a second compound of corundum and a binder, molding this compound around the first compound,hand subjecting the product eat. 4. The method of producing a resistance unit consisting of mixing together 46-80% carbon, 52-12% carbide of boron, binder, molding the mixture into a desired form, subjecting the compound to the action of pressure and heat, mixing a second comound of 85-98% corundum and 15-2% inder, molding this compound around the first compound, and subjecting the product to the action of pressure and heat.

5. The method of producing a resistance unit consisting of mixing together 46-80% carbon, 52-12% carbide of boron, and 2-8% sodium silicate, molding the mixture into a desired form, subjecting the compound to the action of pressure and heat, mixing a second com und of 85-98% corundum and 15-2% sodium silicate, molding a comund around the first compound, and subecting the product to the action of pressure and heat.

. 6. The method of unit consisting of mixing carbon, 52-12% pulverized carbide of boron, and 2-8% sodium silicate, molding the mixture into a desired form, subjecting the mixture to a high pressure, heating the mixture to a temperature of 1200-1400 F. for 24-48 hours, mixing a second compound of 85-98% corundum and 15-2% sodium silicate, molding this compound around the first compound, subjecting the product to a high pressure, and heating the product to 1800-2000 F. for 18-36 hours.

7. As a new article of manufacture, a resistance unit com rising an inner heating element compose of approximatel 63% carbon, 32% carbide of boron, and 5% inder, and an outer covering for a portion 0 same composed of approximately Sil corundum and 8 5% binder.

and 2- -8% producing a resistance together 46-80% 8. As a new article of manufacture, a re- I .sistanc'e unit comprising an inner heating element com of 46-80% carbon, 52-12% carbide o boron, and 2-8% binder, and an outer covering tor a portion of the same com of an electrical insulating material which will protect the inner heating element from oxidation. v

In testimonywhereof, I aflix my si ature CARROLL H. BO ES.

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